Device and method for offset compensation based on hysteresis tracking
a technology of offset compensation and hysteresis tracking, applied in the field of filter devices, can solve the problems of weak sensor signal, unsuitable direct signal processing with the sensor signal, subject to technical errors, etc., and achieve the effect of adjusting the distance between the upper and lower hysteresis levels and the distance between the hysteresis levels
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first embodiment
FIG. 2 shows a structural view of the low pass filter 130. Thereafter, the electronic filter 130 includes a variable resistor R and a variable capacitor C. The variable resistor R is connected to the input of the electronic filter 130 in series. The variable capacitor C is connected to the output of the electronic filter 130 in parallel. Thus, the variable resistor R and the variable capacitor C are arranged to form a well known low-pass filter.
[0049]The resistance of the variable resistor R can be adjusted by a resistor setting signal sR. The capacitance of the variable capacitor C can be adjusted by a capacitor setting signal sC. Thus, the time constant τ=RC of the low-pass filter 130 according to the first embodiment can be adjusted by amending the resistance of the resistor R and / or by amending the capacitance of the capacitor C. Due to practical reasons, only the capacitance of the capacitor C may be adjustable and the resistance of the resistor R may be kept constant.
The low-p...
second embodiment
[0050]Prior regarding this challenge and its solution in further detail, a second embodiment for the electronic filter 130 as shown in FIG. 3 should be discussed.
[0051]This low-pass filter 130 may include three capacitors C1-C3 connected in parallel. This amount of capacities is chosen arbitrarily. Each parallel connection of the capacitors C1-C3 can be enabled or disabled by a switch provided in each connection line of the parallel connection. Further, the first capacitor C1 is connected to the input of the low pass filter 130 in parallel. Also the parallel connection between the first capacitor C1 and the input of the low-pass filter 130 can be enabled or disabled by a switch provided in both connection lines of the parallel connection. The third capacitor C3 is connected with the output of the low-pass filter 130 without having any switch for disabling or enabling the parallel connection.
[0052]As already mentioned, the amount of three capacitors is chosen arbitrarily. The basic i...
third embodiment
FIG. 9 shows the working principle of the comparator 150 if the comparator is a Schmitt-Trigger. Therein, it is further considered, that the amplified sensor signal uâ may steadily run between the upper hysteresis uu and the lower hysteresis ud. In this case, there would be no crossing points and thus no generation of the measurement signal um, since the measurement signal um keeps unaltered, if it is situated between the upper hysteresis uu and the lower hysteresis ud.
[0075]However, this situation can be prevented by keeping the hysteresis levels constant if the measurement signal um is situated between the upper hysteresis uu and the lower hysteresis ud. As can bee seen from FIG. 9, if the measurement signal um negatively crosses the upper hysteresis level uu at the point T5, the controller 140 will stop changing both hysteresis levels uu, ud and keeps them constant. Since the amplified sensor signal uâ is alternating, it will forcibly cross the lower hysteresis level in point T6....
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